1. Field of the Invention
This invention relates to a plasma resistant member that is used as a constituent member of a semiconductor manufacturing apparatus, a liquid crystal manufacturing apparatus, and the like.
2. Description of the Related Art
In manufacturing semiconductors and liquid crystals, many processes using fluorine plasmas in etching and cleaning wafers and so forth are used. Usually, chamber walls of an apparatus used in these processes are made of aluminum. However, aluminum reacts with fluorine plasma to thereby produce an Al—F compound. This compound is changed into particles that adversely affect devices. To prevent this, hitherto, the reaction to the fluorine plasma has generally been suppressed by using alumina ceramics in the region of a chamber whose plasma exposure conditions are severe, or by providing an alumite coat thereon.
However, with recent enhancement of performance of devices, the use of alumina ceramics and an alumite coat of conventional techniques have caused problems. This is, because of the facts that recent progresses of micro-fabrication have promoted employment of high-vacuum plasma, that thus, alumina exposed to higher-density fluorine plasma are greatly abraded. Consequently, an amount of produced Al—F particles is not ignorable.
The possibilities of using Yttria, YAG (Y3Al5O12), and the like as a member, which produces no Al—F particles, instead of alumina have been considered. There has been a trend toward gradual increase in utilization of Yttria thereamong. In this case, Yttria has also been utilized as bulk ceramics. Alternatively, a surface of an existing material is coated therewith by utilizing thermal spraying. The method of forming an Yttria coat by utilizing the thermal spraying has less influence on the processes and is achieved at relatively low cost. Thus, the use of the plasma-resistant member, the surface of the base material of which is coated with Yttria, gradually increases under present circumstances.
There are various methods, such as a thermal spraying method, a CVD method, and a PVD method, for forming an Y2O3 coat on the surface of the base material. In consideration of the cost and the thickness of the formed layer, the thermal spraying method is evaluated to be highly practical. In the case of using a coating layer formed by the thermal spraying method as a plasma resistant layer, the denseness and the adhesion strength thereof are important factors. If a layer whose denseness is low and porosity is high, the etching rate thereof is high. Further, if a through hole, which reaches the base material, is present in the layer, the layer cannot function as a protective one. In a case where the adhesion strength between the layer and the base material is low, there is a possibility of peel-off thereof due to stress that is generated by energy received from the plasma. The peel-off of the coating layer causes problems that the coating layer becomes a source of particles, and that the base material is exposed.
Japanese Patent Unexamined Publication JP-A-10-45467 discloses corrosion-resistant member, whose part to be exposed to a fluorine-corrosive gas or a plasma thereof is made of a composite oxide including a metal of the group 3a of the periodic table and Al and/or Si. Japanese Patent Unexamined Publication JP-A-11-157916 discloses a corrosion-resistant member, whose part to be exposed to a chlorine-corrosive gas or a plasma thereof is made of a composite oxide including a metal of the group 3a of the periodic table and Al and/or Si.
However, according to a conventional technique of JP-A-10-45467, a part to be exposed to fluorine plasma is made of a composite oxide containing a metal of the group 3a of the periodic table and Si. This composite oxide is a sintered compact of a garnet crystal, such as YAG, a single crystal, such as YAM, a perovskite crystal, and monosilicate. This document does not disclose that a coating layer is formed of Y2O3. Also, conventional technique of JP-A-11-157916 is nearly equivalent to that of JP-A-10-45467. A part, at which a composite oxide is formed, is that to be exposed to a fluorine-corrosive gas or to plasma thereof. Therefore, the conventional technique differs from the present invention in this respect.